First I'd like to recommend making the pouch by mixing two rabbit fur. This is so that you can pick them up instead of eating them outright. Then you can save before eating them, since a couple of them are poisonous.
The six are:
Liberty Cap Mushroom
I found the best place to find them is the forests in the southwest area of the map. A couple of them I also found in the northwest area, right below the snowy parts. A few of them are very small, so hunting for them during the day and keeping your head down is recommended.